occipital and temporal lobe Flashcards
visual perception and memory
What is functional differentiation?
-Where different neuron types or different brain regions process different properties of visual stimuli
What are simple features?
-Light intensity and wavelength
-2D position in visual field
What are the complex visual representations for perception and memory?
-Form, surface, spatial relationships and movement
-Multimodal representations
How are these linked?
-Simple features get combined and elaborated via parallel channels to the complex visual representations for perception and memory
Describe the visual info processing in extra striate cortex
-Neurons signal ‘global’ properties of visual scenes and objects rather than ‘component’ properties
-Holistic global properties such as form in V3 and motion in V5
Describe the idea of global colour
-Perceived colour depends on wavelength reflected by object and surroundings
-E.g. Colour constancy occurs where perceived colour of an object doesn’t change even when viewed in a different light
Describe the idea of component wavelength
-Some neurons in V4 are ‘colour’ sensitive
-Others in primary visual pathway and V2 are only ‘wavelength’ sensitive
Describe the idea of component motion
-Area V5 looks at larger parts of field view and registers true and overall direction
-Only responds to certain orientations of the component
-Best driven by moving/motion stimuli
What can occur if there is inferior temporal lobe lesions?
-Ventral stream
-Impair object discrimination and recognition
What can occur if there is posterior parietal lesions?
-Dorsal stream
-Impairs object location
Describe Mishkin et al (1982) study
-Non-human primates (monkeys)
-Had monkeys do different taks on visual info processing
1: Remember different objects, and point to correct object to get food
2: Visuo-spatial task, animal had to look close to a certain location to get food
-Object task was impaired by lesions to ventral stream
-Visuo-spatial task was unimpaired
What did Milner and Goodale find?
-Ventral stream = visual info for object perception
-Dorsal stream = visual info for visuospatial guided action
What is the evidence of this?
-Patients with occipito-temporal brain damage show forms of visual agnosia (as well as deficits in visual perception without blindness)
-Patients with posterior-parietal lobe lesions show optic ataxia (have relatively intact visual function, deficits in visually guided reading)
Describe the case of Patient DF
-Extensive damage to visual stream
-Profound visual agnosia, but intact visually guided reading
-Can act on visual stimulus e.g. visuomotor posting
-Unable to make perceptual judgements e.g. perceptual orientation matching
Describe visual perception in inferior temporal cortex
-Receives input from extra striate cortex
-Forms final stage in visual processing
-Neurons respond selectively to specific shapes and objects
Describe face cells
-Some neurons in inferior temporal lobe shows highly selective responses to individual faces
-Recognise certain and individual entities
-Began conducting research on monkey faces and then turned to human faces
Describe the Medial Temporal Lobe (MTL)
-End of visual processing hierarchy
-Combines inputs from ventral and dorsal
-Receives visual, auditory, olfactory and other sensory info
-Multi modal representations
What does the primary visual pathway contain?
-V1
What does the extrastriate cortex contain?
-V2
-V3a
-V3
-V4
-V5 (also known as MT)
What does the inferior temporal cortex contain?
-Posterior parietal cortex - dorsal stream that has visual spatial processing
-Superior temporal sulcus (STS) / TE (anterior) / TEO (posterior) - ventral stream that has object analysis
